Clamp for temporary or definitive external orthopaedic fixation, and external fixation system comprising said clamp

ABSTRACT

A clamp applicable to both temporary and definitive orthopaedic external fixation systems comprising a first coupling element having a pair of opposite jaws defining one or more seats to house a first component of the orthopaedic external fixation system. A second coupling element comprises a pair of opposite jaws defining one or more seats to house a second component of the orthopaedic external fixation system. An interconnection pin passes through and connects the first and second coupling elements along an axis of rotation. A fastening means is arranged to bring the clamp from a slack configuration. The first and second coupling elements are relatively rotatable along the axis of rotation to a locked configuration, and are relatively rotatable with each other. These fastening means include manually operable temporary fastening means to temporarily lock the clamp, and definitive fastening means operable with a fastening tool, to definitively lock the clamp.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/441,953 filed Feb. 11, 2011, the disclosure of which is herebyincorporated by reference.

FIELD OF APPLICATION

The present invention applies to the field of orthopaedic surgery and itrelates in particular to a clamp intended for the temporary ordefinitive fixation of the elements composing an external fixationsystem.

The present invention also relates to an external fixation systemcomprising this clamp.

PRIOR ART

In orthopaedics, external fixation techniques for stabilizing, reducingand manipulating bone segments are known and commonly used. Thesetechniques provide the surgical application of an external fixationsystem, composed in its simplest form of a set of rods associated bymeans of endosseous pins or Kirschner wires to the patient's bonestructure. The articulation of rods with respect to each other and tofixators is carried out by suitable clamps.

These fixation systems can be applied temporarily during an operation,or definitively in order to be removed only upon full recovery from thetreated pathological condition.

The use of temporary fixation systems is required especially for thefollowing reasons:

-   -   a patient may have serious lesions that require priority        treatment;    -   a patient may have lesions obliging interventions to be minimal;    -   local conditions in the fracture region could preclude        definitive fracture fixation owing to severe wound infection, or        a lack of covering soft tissue, or a shortage of blood supply;    -   single fractures to be treated may not be particularly serious,        but they may require long and complex surgical interventions for        their treatment if they are taken together with other fractures        that have occurred.

In the latter case some or all of the fractures can be treated by meansof external fixation systems. It is however necessary to avoidsituations wherein one is forced to abandon fracture fixation: at theend of the primary treatment all long bones must be firmly fixed.

Beyond these specific requirements, external fixation systems are mainlyapplied in a definitive way. In the case of definitive fixation,however, a different performance is required of the external fixationsystem when compared to temporary applications. In particular, where anexternal fixation system for temporary application is above all requiredto present flexibility of use and rapidity of fixation, a system that isimplanted in a definitive way must ensure a certain degree of rigidity(see for example Orthofix's device marketed under the name XCaliber,which allows for adjustment of lateral curvature while being able tobeartorsional stress during the initial steps of treatment).

This stability partly derives from the alignment of the fixation systemrods with the axes of the long bones to be treated, and partly from theintrinsic stiffness of the device itself and the number of screws, andfurthermore partly in function of the geometrical configuration of thescrews. A correct configuration will promote rapid healing and a quickrecuperation of mobility.

Given the different requirements of the fixation system for these twoapplications, systems have been used up to now that are dedicated eitherto temporary treatment or to definitive treatment.

This specificity in treatment is undoubtedly one of the disadvantages ofthe external fixation systems known up to now; for example, when atemporary fixation needs to be applied that subsequently must besubstituted by definitive fixation, it is necessary to replace theentire fixation system.

On the other hand, the main critical aspect that stands in the way ofexternal fixation systems for mixed use is to do with the clamp that isintended to fasten joining elements such as rods, screws and Kirschnerwires.

In fact, in cases of temporary fixation it is essential that this clampallows the relative orientation of the elements it connects to berapidly blocked, possibly without using a fastening tool. In definitivefixation, the blocking of the relative orientation must however be rigidand stable over time, features that clash with the above-mentionedfastening modes.

Therefore, the technical problem underlying the present invention is toprovide a clamp that can be used in external fixation systems and thatis suited for both temporary use and definitive use, i.e. that can belocked in a rapid and manual way, but that at the same time ensuresrigidity and stability over time.

SUMMARY OF THE INVENTION

The above-mentioned technical problem is solved by a clamp for anexternal orthopaedic fixation system comprising:

-   -   a first coupling element, comprising a pair of opposite jaws        that together define one or more seats suitable for housing at        least a first component of the external orthopaedic fixation        system;    -   a second coupling element, comprising a pair of opposite jaws        that together define one or more seats suitable for housing at        least a second component of the external orthopaedic fixation        system;    -   an interconnection pin crossing and connecting the first and        second coupling elements along a main axis of rotation;    -   fastening means arranged to bring the clamp from a slack        configuration, wherein the first and second coupling elements        are relatively rotatable at least along the main axis of        rotation, to a locked configuration, wherein the first and        second coupling elements are relatively integral with each        other; these fastening means comprising in particular:    -   temporary fastening means, which can be manually operated,        arranged to bring the clamp temporarily in a locked        configuration;    -   definitive fastening means, which can be operated by means of a        fastening tool, arranged to bring the clamp definitively in a        locked configuration.

The alternative meanings “temporarily” and “definitively” are intendedto discriminate, similarly to what has been done in the previousdescription of prior art, between a temporary fastening of the clampcomponents and a definitive fastening. The temporary, moderately tightfastening can be rapidly realized without using a fastening wrench; itallows the elements to be relatively fixed but it does not guaranteerigidity and stability of the chosen position over time. Instead thedefinitive fastening, which is stronger than the previous one, is ableto withstand the regular stress that an external fixation system isexposed to in the course of a patient's treatment.

A person skilled in the art will immediately note how the presence ofdouble fastening means on the clamp, the manual ones and those that arefastened by means of a tool, allows the device to be applied to externalfracture fixation systems with the result that these systems will besuited for both temporary and definitive use.

Moreover it should be noted that, although the capabilities of the clampaccording to the present invention are greatly adapted to the context ofan external fixation system for both temporary and definitive use, thisclamp can advantageously be used in any other orthopaedic application.

The above-mentioned temporary fastening means can advantageouslycomprise a fastening ring nut, arranged to fasten the first and secondcoupling elements to each other along the length of the clamp'sinterconnection pin.

In particular, the fastening ring nut can advantageously have acylindrical peripheral handling surface that is conveniently knurled.

The single jaws of at least one of the pair of jaws can be both crossedby the interconnection pin, so that this pair of jaws is not fastened inthe slack configuration of the clamp and fastened in the lockedconfiguration of the clamp.

This configuration results in an advantageous acceleration of clamplocking operations, since the same means are used both to fasten thejaws and to fix the coupling elements.

The clamp can further comprise a spring interposed between the first andsecond coupling elements, which can advantageously determine apre-fastening action of the jaws of the coupling element onto therespective seats.

In a first embodiment of the clamp according to the present invention,the fastening ring nut can engage a threaded end of the interconnectionpin, the opposite end of said interconnection pin being constrained tothe first coupling element, the second coupling element being interposedbetween the fastening ring nut and the first coupling element.

In alternative embodiments of the clamp, instead, the fastening ring nutis axially constrained to one end of the interconnection pin, theopposite end being threaded and engaging an at least partially threadedhole of the second coupling element, said first coupling element beinginterposed between the fastening ring nut and the second couplingelement.

In one of these embodiments, which presents the advantage of greatstructural simplicity, the fastening ring nut even defines a fasteninghead that is integral with the interconnection pin, said definitivefastening means comprising a hollow in said head intended to allow it toreceive a fastening tool.

In particular, the fastening ring nut can surround a connecting rod headof the interconnection pin, said definitive locking means comprising aneccentric body, rotatably mounted on the fastening ring nut whichcrosses said connecting rod head along an axis perpendicular to the mainaxis of rotation, the rotation of said eccentric body with respect tothe fastening ring nut creating a translation of the end of theinterconnection pin engaged in the second coupling element towards thefastening ring nut.

In some embodiments of the clamp, said definitive fastening meanscomprise an eccentric body, rotatably mounted on a hinging member thatis axially integral with either one of the first and second couplingelements, said eccentric body crossing a connecting rod head of theinterconnection pin along an axis perpendicular to the main axis ofrotation, the opposite end of said interconnection pin being constrainedto the other between the first and second coupling elements, therotation of said eccentric body with respect to the hinging bodypromoting a translation of the opposite end of the interconnection pintowards said hinging body and a subsequent relative approach of the twocoupling elements.

In one of these embodiments, the fastening ring nut is arranged inabutment against the outermost jaw of the second coupling element, saidhinging body corresponding to the first coupling element, the end of theinterconnection pin opposite the connecting rod head being threaded andconstrained by screwing to the fastening ring nut.

In an alternative embodiment, said eccentric body hinges the firstcoupling element to the interconnection pin along a secondary axis ofrotation, advantageously defining a second degree of rotational freedombetween the first coupling element and the second coupling element inthe slack configuration of the clamp.

The eccentric body can then be hinged onto a base portion that proceedsin the direction of the second coupling element as a protuberance of theinnermost jaw of the first coupling element.

In this case, a central joint crossed by the interconnection pin can beadvantageously arranged between the base portion and the second couplingelement, said central joint having a sliding face along a concaveperiphery of the base portion and a flat face intended to couple with asurface of the internal jaw of the coupling element.

The above-identified technical problem is also solved by an externalorthopaedic fixation system comprising at least one of theabove-described clamps, besides known rods and fixators.

This external orthopaedic fixation system can further comprise at leastan innovatively designed wire-carrier element, arranged to allow atleast one Kirschner wire or other fixator of limited-diameter to befixed onto one of the system clamps.

One should note that this wire-carrier element can also beadvantageously applied outside the scope defined by the presentinvention, as it presents innovative features of its own.

The wire-carrier element can comprise a shank with a threaded portiononto which a fastening plate is screwed right up to an abutting platethat is integral with the shank.

The shank can comprise a gripping portion intended to be locked betweenthe jaws of one of the system clamps.

The fastening plate can further advantageously have four peripheralteeth on one of its faces turned towards the abutting plate,equiangularly spaced along the circumference of said plate and arrangedto abut against a flat surface of the abutting plate, thus defining, incollaboration with the shank portion comprised between the two plates, aseat for a Kirschner wire or for screws of limited diameter.

Further features and advantages will be apparent from the followingdescription of some preferred, but not exclusive, embodiments of thepresent invention, with reference to the attached drawings, given by wayof non-limiting examples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axonometric view of a clamp according to the invention;

FIG. 2 is a sectional view along a vertical central plane of the clampof FIG. 1;

FIG. 3 is a sectional view, taken along the line of FIG. 2, of the clampof FIG. 1;

FIGS. 4 and 5 are respective axonometric views of a clamp according toan alternative embodiment of the present invention;

FIG. 6 is a sectional view along the line VI-VI of FIG. 7 of the clampof FIGS. 4 and 5;

FIG. 7 is a sectional view, taken along the line VII-VII of FIG. 6, ofthe clamp of FIGS. 4 and 5;

FIGS. 8 and 9 are respective axonometric views of a clamp according to athird embodiment of the present invention;

FIG. 10 is a sectional view along a vertical central plane of the clampof FIGS. 8 and 9;

FIG. 11 is an axonometric view of an element of an external fixationsystem according to the present invention;

FIG. 12 is a sectional view, taken along a vertical central plane, ofthe element of FIG. 11;

FIG. 13 is an axonometric view of an external fixation system accordingto the present invention applied to a first bone site of a patient;

FIG. 14 is an axonometric view of an external fixation system accordingto the present invention applied to a second bone site of a patient.

DETAILED DESCRIPTION

According to a first embodiment of the present invention, FIGS. 1-3 showa first clamp, globally indicated with reference number 1, for anexternal modular fixation system suitable to be used for the treatmentof lower limb bones, such as tibia, femur or pelvis. Through a simpledimensional adjustment it is possible to use this clamp also for upperlimb bones, for example a humerus.

In this first embodiment, the clamp allows a rod and a plurality ofendosseous pins to be fixed in a simple and stable way, as will be clearfrom the following description.

The clamp 1 comprises a first multi-seat coupling element 2 for fixingendosseous pins, comprising at least three seats to fasten as manyendosseous pins.

The multi-seat coupling element 2 is preferably made of metal.

According to the present invention, the multi-seat coupling element 2comprises an upper jaw 3 and a lower jaw 4. The upper jaw 3 performs thefunction of a lid and has a pair of through-holes, at least partiallythreaded, through which closing screws 13 pass. The lower jaw 4comprises a corresponding pair of internally-threaded blind holes toreceive the ends of the two screws 13.

At least an insert 5 is provided in at least one of the seats in orderto fix the endosseous pins. In particular, the use of inserts of ahemispheric form is provided between the lower jaw 4 and the upper jaw 3in order to define each housing seat of the endosseous pins.

These inserts 5 are made of a different material with respect to thejaws 3 and 4, for example out of a non-conductive material.

More particularly, it is preferable that these inserts are made of aradiotransparent material that is MRI-compatible.

In the example shown, the three seats are equidistant, the central seatis placed in correspondence with the central axis and the two remainingseats are on either side thereof.

A base portion 6 developing as a protuberance of the lower jaw 4 has aseat internally to house the head of an interconnection pin 7 shaped asa connecting rod with a shank extending along a main axis of rotation x,which is orthogonal to the seats defined by the first coupling element2, towards a second rod coupling element 8.

The second rod coupling element 8 also has a lower jaw 9 and an upperjaw 10.

This second rod coupling element 8 has a single C-shaped seat, lateraland orthogonal with respect to the main axis of rotation x, forsnap-fitting it to a fixing rod 100.

The lower and upper jaws 9, 10 of the second coupling element have acentral through-hole through which the interconnection pin 7 passes.

A fastening ring nut 14, suitably knurled on the outside for bettergrip, is screwed on the free end of the interconnection pin 7. Inparticular, this ring nut 14 has a threaded central hole that is screwedon the end of said interconnection pin 7.

A washer 15 through which the interconnection pin 7 passes, is insertedbetween the lower jaw 9 of the second coupling element 8 and the ringnut 14.

In brief, the first multi-seat coupling element 2 is mounted onto thehead of the interconnection pin 7. It is able to move freely andangularly, while the second rod coupling element 8 is rotatably mountedonto the interconnection pin 7.

A spring 11 is inserted between the first multi-seat coupling element 2and the second rod coupling element 8 around the interconnection pin 7.This spring 11 is compressed between the lower jaw 4 of the firstcoupling element 2 and the upper jaw 10 of the second coupling element 8and concealingly housed in impressions on the opposite surfaces of thesejaws. The spring 11 defines a spring-loaded fastening force exerted bythe jaws on the elements inserted into the seats of the couplingelements before locking the clamp.

Moreover, a central joint 16 with a central hole for the passage of theinterconnection pin 7 is placed between the two coupling elements 2 and3.

In order to avoid sliding during the usual assembly operations,respective anti-rotation means 17 are present on the surface of theupper jaw 10 of the second coupling element 8 and on the surface of thecentral joint 16; in the example these means are formed integrally withthe body of the piece itself and they comprise a plurality of radiallyoriented grooves on a crown placed around the central hole.

Advantageously, the head of the interconnection pin 7 has a through-holeto allow an eccentric body 12 to be transversely inserted along asecondary axis of rotation y into a bush 19. This eccentric body 12 has,on the two opposite sides accessible from the outside, on the sides ofthe lower jaw 4 of the first coupling element 2, respective hollowsocket heads 18 to receive a control socket wrench.

The simple rotation of the eccentric body 12 allows it to be locked inits seat and at the same time to bring the free end of theinterconnection pin 7 nearer the first coupling element 2, thus defininga relative locking of the various elements of which clamp 1 is composed.

The clamp 1 can have a slack configuration in which the jaws of thesecond coupling element 8 are not fastened, the second coupling element8 is rotatable with respect to the interconnection pin 7 along the mainaxis of rotation x and the axis of the interconnection pin 7 isrotatable with respect to the first coupling element 2 along thesecondary axis of rotation y. In this slack configuration, therefore,two degrees of rotational freedom are present, together allowing for aproper relative positioning of the first coupling element 2 and thesecond coupling element 8. In alternative the clamp 1 can have a lockedconfiguration in which the two coupling elements 2, 8 are relativelyintegral with each other and the jaws of the second coupling element 8are fastened. It should be noted that the jaws of the first couplingelement 2 are independent, since the fastening thereof is done by theclosing screws 13 that are autonomous with respect to theinterconnection pin 7.

The manual fastening of the fastening ring nut 14 allows the whole clamp1 to be rapidly pre-closed with no need to use a wrench. This operationbrings the clamp 1 from the slack configuration to a temporary lockedconfiguration, which ensures the fastening of the jaws of the secondcoupling element and the relative locking of the two coupling elements,but does not ensure rigidity and stability over time of theseconditions.

Then, in order to change to a definitive locked configuration, in whichrigidity and stability over time are ensured, it is necessary to rotatethe eccentric body 12 by means of a control socket wrench.

The clamp according to the first embodiment described above has severaladvantages, such as:

-   -   the use of a single clamp to connect the rod and endosseous        pins;    -   the presence of two distinct degrees of rotational freedom for        an easy relative positioning of the coupling elements;    -   the option of manual pre-closure;    -   the possibility to perform the fastening by a single rapid        movement of the control wrench;    -   the compatibility with MRI techniques.

When the clamp according to the first embodiment just described is usedfor upper limbs, it is possible to use the rod coupling element 8 inorder to fix an endosseous pin, simply by changing the size of thevarious elements.

Therefore, where reference has been made to a rod coupling element, oneshould consider that this also comprises endosseous pin couplingelements.

According to a second embodiment of the present invention, FIGS. 4-7show a second clamp, globally indicated with 20, suitable to be used forthe treatment of lower limb bones, such as tibia, femur or pelvis. Aftera simple modification of the dimensions it is also possible to use thisclamp for upper limb bones, for example humerus and forearm, as well asfor treatments of the foot and ankle.

The second clamp comprises a first two-seat coupling element 21comprising an upper jaw 22 and a lower jaw 23, both provided with acentral through-hole for an interconnection pin 24 that extends along amain axis of rotation x′.

The two-seat coupling element 21 has, opposite each other on the twosides of the central hole, two open C-shaped seats to respectively housean endosseous pin and a rod. Again it is possible to adapt thedimensions of said opposite open seats, so that both seats are able tohouse a respective endosseous pin.

The open seats are therefore placed in an eccentric and orthogonalmanner with respect to the main axis of rotation x′.

An insert 25 is provided between the upper jaw 22 and the lower jaw 23on the jaw portion that is intended to house the endosseous pin.

This insert is made of a different material than the material used torealize the two-seat coupling element 21, in particular a non-conductivematerial, when the coupling element is preferably made of steel.

More particularly, it is preferable that this insert is made of aradiotransparent material that is MRI-compatible.

The clamp according to the second embodiment of the present inventionfurther comprises a second coupling element 31 having a lower jaw 33 andan upper jaw 34.

This second coupling element has a single lateral C-shaped seat forclamping between the jaws.

These lower 33 and upper 34 jaws of the second coupling element 31 ofthe clamp 20 also have a central through-hole to allow theinterconnection pin 24 to pass through.

This interconnection pin 24 has at its free end a threading that matchesa corresponding internal threading that is present at least partially inthe through-hole of the lower jaw 33 of the second coupling element 31.

In this manner the first two-seat coupling element 21 is rotatablymounted with respect to the interconnection pin 24, while the secondcoupling element 31 is rotatably constrained to the interconnection pin24 to which it is screwed by means of its own lower jaw 33.

Basically the lower jaw 33 functions like a nut into which the entiresecond clamp 20 can be screwed.

A spring 26 is inserted between the first two-seat coupling element 21and the second coupling element 31 around the interconnection pin 24.This spring 26 is compressed between the lower jaw 23 of the firsttwo-seat coupling element 21 and the upper jaw 34 of the second couplingelement 31, and concealingly housed in impressions on the oppositesurfaces of these jaws. The spring defines a spring-loaded fasteningforce exerted by the jaws on the elements inserted into the seats of thecoupling elements before locking the clamp.

In order to avoid sliding during the usual assembly operations,respective anti-rotation means 27 are present on the opposite surfacesof the upper jaw 34 of the second coupling element 31 and of the lowerjaw 23 of the first coupling element 21; in the example these means areformed integrally with the body of the piece itself and they comprise aplurality of radially oriented grooves on a crown placed around thecentral hole.

Advantageously, the end of the interconnection pin 24 opposite the onethat is screwed on the second coupling element 31 has an enlargementwith the shape of a connecting rod head. This connecting rod head has athrough-hole to allow an eccentric body 28 to be transversely insertedwith the interposition of a bush 30. This eccentric body 28 has, on thetwo opposite sides, a hollow socket head 29 to receive a control socketwrench.

A manually rotatable ring nut 35, through which the eccentric body 28passes as well, encloses the head of the interconnection pin 24. Inparticular, this ring nut 35 has a central slot into which the head ofthe interconnection pin 24 fits perfectly and a central hole throughwhich the shank of the interconnection pin 24 passes.

It should be noted that the rotation of the eccentric body 28 in thering nut 35 allows it to be locked and at the same time allows thesecond coupling element 31 to be pressed against the first two-seatcoupling element 21, thus defining a relative locking between thevarious elements of which the clamp 20 is composed.

A washer 32 through which the interconnection pin 24 passes, is insertedbetween the ring nut 35 and the upper jaw 22 of the first two-seatcoupling element 21.

The clamp 20 can have a slack configuration in which the jaws of thecoupling elements 21, 31 are not fastened and the first two-seatcoupling element 21 is rotating with respect to the second couplingelement 31 around the main axis of rotation x′. In this slackconfiguration, therefore, a degree of rotational freedom is defined thatallows the first two-seat coupling element 21 and of the second couplingelement 31 to be positioned properly relative to each other. Inalternative, the clamp 20 can have a locked configuration in which thejaws are fastened and the two coupling elements 21, 31 are integral withone other.

The manual fastening of the fastening ring nut 35 allows the whole clamp20 to be rapidly pre-closed with no need to use a wrench. This operationbrings the clamp 20 from the slack configuration to a temporary lockedconfiguration, which ensures the fastening of the jaws and the relativelocking of the two coupling elements, but does not ensure the rigidityand stability over time of these conditions.

Then, in order to change to a definitive locked configuration, in whichrigidity and stability over time are ensured, it is necessary to rotatethe eccentric body 28 by means of a control socket wrench.

The clamp according to the second embodiment has several advantages,such as:

-   -   the use of a single clamp to connect two rods or a rod to an        endosseous pin;    -   the presence of a degree of rotational freedom for an easy        relative positioning of the coupling elements; the option of        manual pre-closure;    -   the possibility to perform the fastening by a single rapid        movement of the control wrench;    -   the compatibility with MRI techniques.

According to a third embodiment of the present invention, FIGS. 8-10show a third clamp, globally indicated with 40, suitable to be used forthe treatment of upper limbs, such as wrist, shoulder, hands.

The third clamp comprises a first two-seat coupling element 41comprising an upper jaw 42 and a lower jaw 43, both provided with acentral through-hole to allow an interconnection pin 44 orientated alonga main axis of rotation x″ to pass through.

The two-seat coupling element 41 has, next to the central hole andopposite to each other, open C-shaped seats to respectively house anendosseous pin 101 and a rod. It is also possible to modify thedimensions of these seats so that both are able to house an endosseouspin.

The open seats are therefore placed in an eccentric and orthogonalmanner with respect to the main axis of rotation x″.

An insert 45 is provided between the upper jaw 42 and the lower jaw 43on the jaw portion that is intended to house the endosseous pin.

This insert is made of a different material than the material being usedto realize the coupling element 41, in particular a non-conductivematerial, when the coupling element 41 is preferably made of steel.

More particularly, it is preferable that this insert 45 is made of aradiotransparent material that is MRI-compatible.

The third clamp 40 according to the present invention further comprisesa second coupling element 46 having a lower jaw 47 and an upper jaw 48.

This second coupling element has a single opening for clamping a rod 100between the jaws.

These lower 47 and upper 48 jaws of the second coupling element 41 ofthe third clamp 40 also have a central through-hole to allow theinterconnection pin 44 to pass through.

This interconnection pin 44 has at its free end a threading that matchesa corresponding internal threading that is present at least partially inthe through-hole of the lower jaw 47 of the second coupling element 46.

In this manner the first two-seat coupling element 41 is rotatablymounted with respect to the interconnection pin 44, while the secondcoupling element 46 is rotatably constrained to the interconnection pin44 to which it is screwed by means of its own lower jaw 47.

Basically the lower jaw 47 functions like a nut into which the entirethird clamp 40 can be screwed.

A spring 49 is inserted between the first two-seat coupling element 41and the second coupling element 46 around the interconnection pin 44.This spring 49 is compressed between the lower jaw 43 of the firsttwo-seat coupling element 41 and the upper jaw 48 of the second couplingelement 46, and concealingly housed in impressions on the oppositesurfaces of these jaws. The spring 49 defines a spring-loaded fasteningforce exerted by the jaws on the elements inserted into the seats of thecoupling elements before locking the clamp.

In order to avoid sliding during the usual assembly operations,respective anti-rotation means 50 are present on the surface of theupper jaw 48 of the second coupling element 46 and on the surface of thelower jaw 43 of the first coupling element 41; in the example thesemeans are formed integrally with the body of the piece itself to whichit is fixed and they comprise a plurality of radially oriented grooveson a crown placed around the central hole.

The end of the interconnection pin 44 opposite the one that is screwedon the second coupling element 46 has an expansion that is shaped like aplanar fastening ring nut 51 that can be operated manually from theoutside. In the middle of its free surface this fastening ring nut 51has a socket hollow 53 to receive a control socket wrench.

A washer 52 through which the interconnection pin 44 passes, is insertedbetween the fastening ring nut 51 of the interconnection pin 44 and theupper jaw 42 of the first two-seat coupling element 41.

The third clamp 40 can have a slack configuration in which the jaws ofthe two coupling elements 41, 46 are not fastened and the first two-seatcoupling element 21 is rotatable with respect to the second couplingelement 46 around the main axis of rotation x″. In this slackconfiguration therefore a degree of rotational freedom is defined thatallows the first two-seat coupling element 41 and the second couplingelement 46 to be positioned properly relative to each other. Inalternative, the clamp 40 can have a locked configuration in which thetwo coupling elements 41, 46 are integral with one other and their jawsare fastened.

The manual fastening of the fastening ring nut 51 allows the whole clamp40 to be rapidly pre-closed with no need to use a control socket wrench.This operation brings the clamp 40 from the slack configuration to atemporary locked configuration, which ensures the fastening of the jawsand the relative locking of the two coupling elements, but does notensure the rigidity and stability over time of these conditions.

Then, in order to change to a definitive locked configuration, in whichrigidity and stability over time are ensured, it is necessary to inserta control socket wrench into the socket hollow 53 of the fastening ringnut 51 and to fasten it by means of this tool.

The clamp according to the third embodiment has several advantages, suchas:

-   -   the use of a single clamp to connect two rods or a rod to an        endosseous pin;    -   the presence of a degree of rotational freedom for an easy        relative positioning of the coupling elements;    -   the option of manual pre-closure;    -   the compatibility with MRI techniques.

The modular external fixation system 200, 300 according to the presentinvention, shown in FIGS. 13 and 14, can comprise one or more of theabove-described clamps 1, 20, 40; moreover it can comprise awire-carrier element 60 of the type shown in the attached FIGS. 11-12.

This wire-carrier element 60, which is particularly useful in fixationsystems for bone sites of the wrist and shoulder, allows one or twoKirschner wires to be supported or alternatively as many screws 102 ofreduced diameter (D=2.5 mm), partially or fully threaded.

The wire-carrier element 60 comprises a shank 61 and a fastening plate62.

The main shank has a threaded portion 63, onto which said fasteningplate 62 is screwed, and a non-threaded gripping portion 64; the twoportions are divided by an abutting plate 65.

The fastening plate 62 has on its surface turned towards the abuttingplate 65, when in use, four peripheral teeth 68, equiangularly spacedalong the circumference of said plate.

When screwing the fastening plate 62 onto the threaded portion 63 of theshank 61, the four peripheral teeth 68 abut against a flat surface ofthe abutting plate 65, thus defining wire seats in collaboration withthe shank 61 portion connecting the two plates.

Both the shank 61 and the fastening plate 62 comprise hexagonally shapedportions 66 on the external surface of the fastening/abutting plates forthe insertion of a control wrench. The shank 61 also comprises ahexagonal hollow 67 located at the end of its gripping portion 64.

In order to insert a wire or a screw in the wire-carrier element 60, thewire or the screw is inserted in the channel defined by two peripheralteeth 68 on one side and by the shank 61 on the other side; a secondwire or a second screw is then inserted in the channel defined on theother side of the shank by the peripheral teeth 68 opposite the firstones. A pair of parallel wires or screws can thus be associated to thewire-carrier element 60.

In order to associate the wire-carrier element 60 to the rest of theexternal fixation system, it is sufficient to lock its gripping portion64 inside a coupling element of one of the system clamps.

The wire-carrier element described above has several advantages, suchas:

-   -   the possibility to use a normal clamp to connect rods or        endosseous pins to Kirschner wires or screws of limited        diameter;    -   the possibility of an easy relative positioning of the elements        to be connected;    -   the secure fixing of wires or screws locked by the wire-carrier        element;    -   the great structural simplicity of the wire-carrier element,        which consists of only two components.

Modular external fixation systems 200, 300 according to the presentinvention, which can be seen in two alternative embodiments in FIGS. 13and 14, comprise, in addition to the above-described innovativecomponents, rods 100 and endosseous pins 101, 102 of the known type.

1. A clamp for an orthopaedic external fixation system comprising: afirst coupling element, comprising a pair of opposite jaws togetherdefining one or more seats able to house at least a first component ofthe orthopaedic external fixation system; a second coupling element,comprising a pair of opposite jaws together defining one or more seatsable to house at least a second component of the orthopaedic externalfixation system; an interconnection pin that passes through and connectsthe first and second coupling elements along a main axis of rotation;fastening means arranged to bring the clamp from a slack configuration,in which the first and second coupling elements are relatively rotatableat least along the main axis of rotation, to a locked configuration, inwhich the first and second coupling elements are relatively integralwith each other; wherein said fastening means comprise: temporaryfastening means, manually operable, arranged to temporarily bring theclamp in the locked configuration; definitive fastening means, operableby means of a fastening tool, arranged to definitively bring the clampin the locked configuration.
 2. The clamp according to claim 1, whereinsaid temporary fastening means comprise a fastening ring nut arranged tofasten together the first and second coupling elements along theinterconnection pin.
 3. The clamp according to claim 2, wherein saidfastening ring nut has a cylindrical peripheral handling surface.
 4. Theclamp according to claim 3, wherein said cylindrical peripheral handlingsurface is knurled.
 5. The clamp according to claim 1, wherein theinterconnection pin passes through both single jaws of at least one ofthe pairs of jaws, said pair of jaws as a result not being fastened inthe slack configuration of the clamp and fastened in the lockedconfiguration of the clamp.
 6. The clamp according to claim 5, furthercomprising a spring interposed between the first and second couplingelements.
 7. The clamp according to claim 4, wherein said fastening ringnut engages a threaded end of the interconnection pin, the opposite endof said interconnection pin being constrained to the first couplingelement, the second coupling element being interposed between thefastening ring nut and the first coupling element.
 8. The clampaccording to claim 4, wherein said fastening ring nut is axiallyconstrained to an end of the interconnection pin, the opposite end beingthreaded and engaging an at least partially threaded hole of the secondcoupling element, said first coupling element being interposed betweenthe fastening ring nut and the second coupling element.
 9. The clampaccording to claim 8, wherein said fastening ring nut defines afastening head that is integral with the interconnection pin, saiddefinitive fastening means comprising a hollow of said head intended toallow it to be coupled with a fastening tool.
 10. The clamp according toclaim 8, wherein said fastening ring nut encloses a connecting rod headof the interconnection pin, said definitive locking means comprising aneccentric body, rotatably mounted on the fastening ring nut, that passesthrough said connecting rod head along an axis that is perpendicular tothe main axis of rotation, the rotation of said eccentric body withrespect to the fastening ring nut promoting a translation of the end ofthe interconnection pin engaged in the second coupling element towardsthe fastening ring nut.
 11. The clamp according to claim 2, wherein saiddefinitive fastening means comprise an eccentric body, rotatably mountedon a hinging body that is axially integral with either one of the firstor of the second coupling elements, said eccentric body passing througha connecting rod head of the interconnection pin along an axis that isperpendicular to the main axis of rotation, the opposite end of saidinterconnection pin being constrained to the other between the first andsecond coupling elements, the rotation of said eccentric body withrespect to the hinging body promoting a translation of the opposite endof the interconnection pin towards said hinging body and as a result torelatively bring the two coupling elements nearer each other.
 12. Theclamp according to claim 11, wherein said fastening ring nut abutsagainst the outermost jaw of the second coupling element, said hingingbody corresponding to the first coupling element, the end of theinterconnection pin opposite the connecting rod head being threaded andconstrained by screwing to the fastening ring nut.
 13. The clampaccording to claim 12, wherein said eccentric body hinges the firstcoupling element to the interconnection pin along a secondary axis ofrotation, defining a second degree of rotational freedom between thefirst coupling element and the second coupling element in the slackconfiguration of the clamp.
 14. The clamp according to claim 13, whereinsaid eccentric body is hinged on a base portion developing towards thesecond coupling element as a protuberance of the innermost jaw of thefirst coupling element.
 15. The clamp according to claim 14, wherein acentral joint is placed between the base portion and the second couplingelement, through which the interconnection pin passes, said centraljoint presenting a sliding face along a concave periphery of the baseportion and a flat face intended to couple with a surface of theinternal jaw of the coupling element.
 16. An orthopaedic externalfixation system comprising a clamp for an orthopaedic external fixationsystem comprising: a first coupling element, comprising a pair ofopposite jaws together defining one or more seats able to house at leasta first component of the orthopaedic external fixation system; a secondcoupling element, comprising a pair of opposite jaws together definingone or more seats able to house at least a second component of theorthopaedic external fixation system; an interconnection pin that passesthrough and connects the first and second coupling elements along a mainaxis of rotation; fastening means arranged to bring the clamp from aslack configuration, in which the first and second coupling elements arerelatively rotatable at least along the main axis of rotation, to alocked configuration, in which the first and second coupling elementsare relatively integral with each other; wherein said fastening meanscomprise: temporary fastening means, manually operable, arranged totemporarily bring the clamp in the locked configuration; definitivefastening means, operable by means of a fastening tool, arranged todefinitively bring the clamp in the locked configuration.
 17. Theorthopaedic external fixation system according to claim 16, furthercomprising at least a wire-carrier element, arranged to allow at least aKirschner wire or other fixator of limited diameter to be fixed to oneof the system clamps.
 18. The orthopaedic external fixation systemaccording to claim 17, wherein said wire-carrier element comprises ashank with a threaded portion whereon a fastening plate is screwed untilit abuts against an abutting plate that is integral with the shank. 19.The orthopaedic external fixation system according to claim 18, whereinsaid shank comprises a gripping portion intended to be locked betweenthe jaws of one of the system clamps.
 20. The orthopaedic externalfixation system according to claim 19, wherein the fastening plate has,on one of its faces turned towards the abutting plate, four peripheralteeth, equiangularly spaced along the circumference of said plate andarranged to abut against a flat surface of the abutting plate, defining,in collaboration with the shank portion comprised between the twoplates, a seat for a Kirschner wire or other fixator of limiteddiameter.